Unauthorized copying of media subject to copyright has been a significant problem throughout the digital age. The ease with which digital media is copied, and often perfectly copied, has fueled the growth of the piracy industry. Often it is difficult to trace the source of an unauthorized copy of a digital audio or video work. Accordingly, it has become commonplace to insert watermarks into digital works to assist in identifying their origin. The watermarks may be inaudible code within an audio file, or changes to an image or series or images in a video that will not be noticeably visible to the viewer.
In some implementations, at the time of downloading or streaming a system will insert a dynamic watermark ID in the media. An example dynamic watermark ID is a concatenation of the MAC address of the downloading device and a timestamp or timecode. This is intended to pinpoint the device and time at which the media was downloaded so as to be able to identify that device as the source of unauthorized copies later if the copies are found to contain the dynamic watermark.
The dynamic watermarks used in existing systems are normally fixed-length bit codes specifying the MAC address and time-code. In some cases, the codes may be 24 bits, 48 bits, 60 bits, or some other fixed-length. The length of these watermarks present robustness challenges for some types of copying and the inclusion of the MAC address presents a potential privacy issue.
Similar reference numerals may have been used in different figures to denote similar components.